Saturday, November 16, 2013



[Ed: I found this article on the internet several years ago and think that the information may help explain in more detail about the AFS and its Facultative anaerobic bacteria and ORP-redox values. There are organisms that can adjust their metabolism to their environment, such as facultative anaerobes. Facultative anaerobes can be active at positive Eh values, and at negative Eh values in the presence of oxygen bearing inorganic compounds, such as nitrates and sulfates, too.]




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This article is based on studies about the Redox Potential as it corresponds to humans and all fish and animals. I have found from practical experience and research that a lot more can be learned from medical studies than from many anecdotal aquarium articles, this is not to say that this research then has to be properly applied and a good aquatic article helps here.

I do not believe this is a subject that many aquarists should stress over, but a lot has been learned about this subject since I first started researching this in the 1980s. However the more I have studied this subject the more I feel that ANY serious aquarist should understand this subject as it has major implications for fish and aquatic health that often go against commonly held anecdotal aquarium keeping beliefs.

I have also had to change my opinions about this subject based on newer evidence. One was should you have a positive or reducing Redox. I based my earlier opinion on a higher Redox of 300 mV based on many studies of ocean waters, but newer human research and my own tests over the last 10 years have lead me to the opposite of -200 to -300. There are some ongoing studies up here in Oregon about BG algae and where a Reducing Redox may help or hinder. All this said, maintaining a good Reducing Redox (for both saltwater and Freshwater) can be as simple as good aquatic husbandry: water changes, proper electrolytes and minor elements in the water, and simple reducers such as Sodium Thiosulfate and Magnesium.

Put another way, maintaining a proper Redox Potential is a lot like having an anti-oxidant vitamin in the aquarium water. The Aquarium Redox is also just one more parameter towards good disease prevention and long term fish health and growth. Please see this article about Aquarium Disease prevention; “Aquarium Disease Prevention” .
Or to be even more blunt; Bleach and Potassium Permanganate are oxidizers (Potassium Permanganate is often used for disease treatment an water clarification is ponds and aquariums), however you would not want your fish living in an oxidizing environment for long term fish health, rather you would want your fish in a Reducing environment where free radicals are not damaging the cells of your fish and causing problems with Osmoregulation. An oxidizing environment is what you get with a positive Redox.

What got me started researching this was I have noticed and documented differences with aquariums (I mostly used goldfish for these tests) with UV sterilizers, added minor elements (such as Wonder Shells) and electrolytes maintaining a Redox Potential around -300-350 mV, but was not sure why health, vitality and especially disease resistance were improved. The goldfish had less incidence of such infestations as anchor worms which UV sterilizers cannot truly eradicate due to difficulty killing them in the UV itself and that Anchor Worms do not get readily caught up in the water column. The Redox Potential explains a lot of the results I was getting.

This pertains to the Redox potential of -300-350 mV that I have found a properly installed and constructed UV aids in maintaining (assuming proper dissolved oxygen levels, and proper mineral levels too, such as kH ). A proper Redox Potential improves the health of humans AND fish. A Redox Potential in the -200-400 mV range in human studies has been shown to have the same affect as anti-oxidant preparations such Vitamin C (and many others). This shows that the health of aquarium fish can be maintained by a UV Sterilizer not just by the killing of potential disease pathogens, but by the maintenance of a proper Redox Potential. I have been observing many aquariums of such "ordinary" fish as goldfish, both with and without UV Sterilizers (keep in mind that some UVs are useless by design and installation), and the goldfish with every other factor equal that had a UV Sterilizer installed, were generally much healthier.

Another interesting aspect of Redox potential is the correlation of a certain Redox level and the growth of Blue Green Algae (Cyanobacteria) in Aquariums and lakes. This is an on-going study however Redox does SEEM to play some role in the aquarium and lake “plague”. For more information about this, I recommend reading this article:
Blue Green Algae (Cyanobacteria) in Aquariums; what it is and how to control it. Currently this is just an opinion though.

I will also note that the aquariums with the proper Redox had the electrolytes present as tested via GH & KH (salt, SeaChem Buffer, & Wonder Shells are a good source), and regular water changes which also resulted in lower nitrate levels (40 ppm or less for FW, 20 ppm or less for SW). I will note that GH is not always a good indicator of Redox as some procedures an products can make your GH test higher than desired (such as in Calcium, Magnesium), but it is in actuality fine as per Redox Reduction

That all said, please read the rest of the article before I over sell any one on a UV Sterilizer or Wonder Shells. As often good aquatic husbandry is all that is necessary for a good Redox Reducing environment.


Redox Potential (oxidation potential) describes the ability for the loss of an electron by a molecule, atom or ion to the gain of an electron by another molecule, atom or ion. Without this positive Redox Potential many minerals cannot be absorbed and properly assimilated. So it is very important to keep a proper Redox Potential (-300 to -350mV) via proper dissolved oxygen levels, UV Sterilization, and proper electrolyte levels (such as magnesium).

Oxidation describes the loss of an electron by a molecule, atom or ion
Reduction describes the gain of an electron by a molecule, atom or ion
The above is a simplification of the process, and much more needs to be considered, please read on.

Oxidized Water:
Oxidized water with its Redox potential of +700 to +800 mV is an oxidizing agent that can withdraw electrons from bacteria and kill them. The oxidized water can be used to clean hands, sterilize utensils, and treat minor wounds.

Here are a few oxidizers: ozone (O3), hydrogen peroxide (H2O2), chlorine (Cl2) and chloramines (NH2Cl).

Reduced Water:

Reduced Ionized with a Redox Potential of -250 to -350 mV readily donates its electrons to unusual oxygen radicals and blocks the interaction of the active oxygen with normal molecules. Substances which have the ability to counteract active oxygen by supplying electrons are called scavengers. Reduced water, therefore, can be called scavenging water. Reduced water inhibits excessive fermentation by reducing indirectly metabolites.

Here are a few reducers, in other words, elements or processes that transfer electrons to another substance;
Magnesium, Calcium, Sodium, and the process of Photosynthesis involves both oxidation and reducing.

As one can see from the graph that elements such as most metals, as well as essential elements for aquatic life: Calcium and Magnesium are major reducers however because of this they are also most easily depleted (the elements at the top and the bottom of the graph are most easily depleted in their oxidation or reducing properties).


Over geologic time abiogenic (not biological in origin), biogenic (produced by living organisms) and anthropogenic (processes are those that are derived from human activities, as opposed to effects or processes that occur in the natural environment without human influences) deposits were accumulated in rivers, lakes and seas. Simultaneously there proceeded the self-purification of natural water on the basis of the chemical reactions of oxidation and reduction. Living organisms such as fish are adapted not to "perfectly clean water", such as distillated water, but to ecologically clean water with definite content of organic and inorganic compounds, micro-admixtures, ions and even bacteria or saprophyte (any plant that depends on dead plant or animal tissue for a source of nutrition and metabolic energy, e.g., most fungi). The range of mentioned components of ecologically clean water is the integral result of oxidation and reduction self-purification of water.

At the initial stages of this cycle toxic hydrophobic organic compounds (molecules that are repelled from a mass of water) are oxidized to the hydrophilic forms (a molecule or portion of a molecule is one that is typically charge-polarized and capable of hydrogen bonding, enabling it to dissolve more readily in water than in oil or other hydrophobic solvents), which are characterized by the better biological compatibility. Energy of oxidation of degrading organic compounds is absorbed during reduction chemical transformations. Excess of ions of the heavy elements transforms into insoluble, inert, nontoxic forms. Concentration of ions of light elements is stabilized. Just in such water live the water organisms, and land animals drink such water.

Spring waters, which are considered to be the most clean according to the ecological criteria, are filtered through the rocks and subjected to the oxidation and reduction, sorption and catalytic influence. As rule, they are mineralized and include non-volatile organic substances, which are detected by the permanganate oxidability (expressed by oxidability by potassium permanganate and potassium dichromate).

After electrochemical purification water keeps its initial neutral values of pH, but ORP (Oxidation Reduction Potential) of water shifts toward the negative (electrode or reduction) values. The resulting purified water obtains the antioxidant properties with characteristics of pharmacological activity close to the properties of the antioxidant preparations (a -tocopherol, b -carotene, vitamin C etc.). In case of dilution of polyvitamin preparations in electrochemically purified water ORP of mixtures is decreased approximately by 200 - 400 mV in relation to the control solutions with non-treated drinking water.

This partially explains how a proper Redox Potential improves the health of the fish or other aquatic organisms as I have observed. Bringing this back to my observations of goldfish aquariums; All aquariums with the same filtration (canister filter with sponge filter), the same feeding schedule and food, even the same basic goldfish (a mix of ryukins and orandas); The aquariums with the quality, properly installed UV Sterilizers (again assuming proper dissolved oxygen levels) not only had less incidence of disease, but general health, appetite, vigor, growth, and water clarity were all improved.

Here is a Quote about pH vs. Redox:

Traditionally we have judged the properties of water from the standpoint of pH, in other words whether water is acidic or alkaline. According to Dr. Yoshiaki Matsuo PhD., the inventor of the Ionized Water unit, "In my opinion, Redox potential is more important than pH. The importance of pH is over emphasized. For example, the average pH of blood is 7.4 and acidosis or alkalosis is defined according to deviation within the range of 7.4 +- 0.005. But nothing has been discussed about ORP, or oxidation-reduction potential."



Another way to look at the Redox Potential in aquariums is to the relation of waste particles and acid production, as well as dissolved oxygen and most importantly depletion of key important elements. The more waste, the less Redox Potential due to more nitric acid production and the depletion of key elements, but this is an over simplification as there is much more to it than this.

You really need to look at the electrolyte balance in your aquarium. Calcium as well as Magnesium are both important reducers, however they are both easily oxidized as well (see the graph in the Redox Potential Basics section). So for proper reduction, these elements need to be replaced.

As stated earlier, Redox is often more important than pH, there are definitely correlations to pH and the Redox effect on pH. But you cannot make the assumption that if you have a pH of 8.0, that you have good reduction. Just like with GH, where your GH is high, you can still have low pH. The bottom line is that there are relations between Redox, GH, pH, and even kH, but these are still individual water parameters.

Also as noted in the beginning of this article, this is not a parameter to stress over, HOWEVER, Redox reduction should NOT be blown off as many anecdotal/uninformed commentators do in many aquatic forums. The more I have studied and observed in this subject, the more I feel it should not be ignored.

Active oxygen molecules, or free radicals, are produced in the water and the fish’ body. They are extremely reactive and can also attach themselves to normal, healthy cells and damage them genetically. These active oxygen radicals steal electrons from normal, healthy biological molecules. This electron theft by active oxygen oxidizes tissue and can cause disease, these are proven facts! This why the constant hammering by some uninformed aquarists against UVs, too high a GH (which is not always a good indicator of electrolyte balance anyway), and even Wonder Shells is ludicrous. Your GH may test higher than desired but in actuality is maintaining a healthy Reducing Redox via Calcium (Facts about Calcium, an essential reducer), Magnesium, ect.

One final note about the Redox Potential; Before it seems that you must rush out and buy a UV Sterilizer to maintain your Redox Potential (this is just one aid that I found to be the easiest and most sure fire, but even UV Sterilization is not enough if the other parameters for proper Redox are out of balance). You can maintain your aquarium’s Redox Potential through these methods:

[1] Proper water changes with ion balanced clean water (electrolytes) with a GH of at least 100- 200 (GH will supply many important reducers such as Magnesium) and with a kH of at least 50-100 ppm. A proper Reducing Redox is another reason for water changes and is also a major reason to not use drinking water drinking water intended for human consumption unless it is properly re-mineralized.

[2] Good aquarium circulation

[3] Or simply an reasonable supply of dissolved oxygen provides by diffusers on power heads or internal filter, air stones, spray bars on the returns of canister filters, ECT. Just make sure you are doing a good job of breaking the surface tension of the water, as this is where gasses, including oxygen are exchanged!

[4] Proper Calcium, Magnesium, sodium, and general electrolyte levels, THIS IS VERY IMPORTANT! (Wonder Shells help here)
I have a good article dealing with kH, Calcium, and Magnesium here:
CALCIUM, KH, AND MAGNESIUM IN AQUARIUMS; How to maintain a Proper KH, why is calcium important

[5] Also ponds with “flow through” or spring fed water sources will maintain a good Redox Potential.

[6] The a UV Sterilizer is one more predictable and proven tool here (when properly installed), but also not a cure all to otherwise poor conditions. UVs work two ways in my research; [1] they morph oxygen (O2) molecules into Ozone (O3), the O3 quickly degrades, the UV then [2] transfers electrons to substances, thus reducing.
As a side note it is the Ozone layer that blocks many harmful UV rays from reaching the Earth, this is due to the reaction of UVC and Ozone high in our atmosphere, so by using a UV Sterilizer (which has safely contained UVC radiation), you break down radicals such as Ozone in your aquarium

For Redox problems, possible problems:

* Driftwood; make sure you soak all Mango Wood or Drift wood for several days in a solution of 2 tablespoons pure salt to 2-5 gallons of water to leach our impurities. Even then if you continue to have problems, remove the wood. Over use of peat can also cause similar problems.

* CO2 generators if not kept at a balance can also cause problems with the Redox Reduction abilities, this is rare, but worth considering. A good link to help here is:
Measuring CO2 levels in a Planted Tank

* An abundance of organic mulm in filters or substrate. Check your cleaning procedures.

* A lack of electrolytes, as mentioned earlier, Wonder Shells can help here, BUT they are not a cure all for other problems.

* A tank with high nitrites and nitrates (nitrates are a mild oxidant) will also tend to be high in nitric acid (but not always); a properly cycled tank is important!

A simple test of Redox can be performed using Methylene Blue and any reducer such as powdered Wonder Shell. Simply add about ½ teaspoon powdered Wonder Shell to 8 oz. of water, stir, then add one drop of Methylene Blue to the solution and stir. The Methylene Blue will dissipate due to the reducer.
Taking this test a step further into the real world, if you add Methylene Blue according to standard dosage to your aquarium water (remove the water for this test), and it stays a brilliant blue, you probably have a positive Redox. If the color dissipates at all (even the slightest) you probably have a reducing number. This test in no way replaces the accuracy of Redox meter, but it is a simple way to get a handle on your aquariums Redox health.


Also this is a relatively unexplored are of fish keeping, and there is still a lot to be learned here and I have to admit having to change my opinions based on newer evidence.

For further information about WHY YOU SHOULD USE A UV STERILIZER

Credit for some of this information:

Another good article about this subject that I found is this: ORP and the Reef Aquarium

Here is a quote from this article” Many aquarists have been lead to believe that ORP is a measure of water quality or purity. Manufacturers selling ozonizers and other oxidizers (like permanganate) have been especially keen to present that idea. But is it really true? Is a higher Redox indicative of "purer water" even when that Redox is manipulated artificially by adding strong oxidizers? Or is such an addition analogous to an air freshener that masks odors? I don't know the answer, but I think that aquarists and pond hobbyist should ask the question, and hope to hear useful answers before adding such materials to their aquaria or ponds.”

This statement is where many aquarists and pond hobbyist have gone wrong in my opinion, A positive Redox is NOT a measure of water quality, but at least a Reducing Redox has more potential for a healthy aquarium.

More references:
Redox and Electrochemistry








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